Sister Monica Joan was one of the first to qualify as a nurse midwife in the United Kingdom. Her birth name is Antonia Keville. She is portrayed by Judy Parfitt.
Sister Monica Joan has a love of literature, astrology, and sweets, particularly cake. When Jenny Lee first arrives at Nonnatus House, she is quick to show off her love for astrology (see Quotes), and to insist that Jenny consume a whole cake with her.
Due to her old age, Sister Monica Joan often gets confused. At the end of the first season, she is taken to court for theft, and during this time, some jewellery is found amongst her belongings, but it turns out the jewellery had belonged to her mother, and Mother Jesu told the court that Sister Monica Joan recognized neither the jewels nor her petty thefts due to her fragility, and the charges were dropped.
Sister Monica Joan often fears she is old and useless and expresses a desire to help. In one episode in Season Four she gets her chance when a heavily pregnant woman in labour arrives at Nonnatus House looking for help and since the only available midwife, Trixie, has passed out from drinking too much alcohol, Sister Monica Joan has to take matters into her own hands. She takes the woman to Dr. Turner's surgery, where Shelagh helps to deliver the woman's child, and the woman shows the elderly nun her gratitude by naming her baby girl Monica, and she is deeply moved by the gesture.
Sister Monica Joan came from a very well-to-do family who didn't approve of her pursuit of a midwifery career nor did they support her in her subsequent entry into the religious life. Her difficulties with her family have been referred to frequently throughout the series although she does reconcile with her nephew and his family in Season Two.
When Sister Monica Joan entered into the religious life she had not a penny to her name. When her mother died she left her some of her jewellery which was given to the Order when she took her final vows in 1904. These were the jewels that Sister Monica Joan was accused of stealing in the Season One finale but Mother Jesu tells the court she gave her the jewels as "balm for an old wound".